A Phase I study of recombinant human IL-12 in patients with advanced malignancies. The end points are assessments of dosing against toxicity, pharmacology immunologic effects, and possible suppression of tumor growth. The study will be conducted at 4 centers with a maximum of 42 patients with 10-15 from NEMC anticipated. IL-12 naturally occurring cytokine which has been shown to have multiple effects in vitro including to enhance NK cell activity, to stimulate proliferation of T lymphocytes and NK cells.